Vehicle emissions standards have become increasingly stringent due to knowledge of the negative environmental effects of hydrocarbon emissions, which are generated by fuel vapors released into the atmosphere. For vehicles and other fuel-operated devices, controlling and containing fuel vapors is important to reduce emissions. Vehicles contain an on-board diagnostic system that monitors whether the fuel system is completely vapor-tight.
The refueling process requires a user to remove a closure, such as a gas cap, which seals a filler neck in the fuel system when the gas cap is screwed over or onto the filler neck. Screwing and unscrewing the gas cap requires the user to undergo several different steps and motions during the refueling process that must either be conducted with two hands or as separate steps (i.e., it is difficult to unscrew a gas cap and hold a refueling nozzle using the same hand at the same time). Although gas caps having doors or other openings have been proposed in the past, these structures do not form the seals required to meet current stringent emissions requirements. Moreover, these structures tend to leave the opening of the filler neck and any associated flapper door exposed to potentially corrosive environmental contaminants, such as mud, rain, dust, etc.
Further, in areas where both diesel fuel and conventional gasoline are both used as fuels, it is possible for a user in a hurry to mistakenly insert a gasoline fuel nozzle into a diesel fuel filler neck because a gasoline fuel nozzle has a smaller diameter than a diesel fuel nozzle.
There is a desire for a structure that can protect an opening in a filler neck from environmental contaminants while allowing the structure to be easily manipulated by the fuel nozzle alone. There is also a desire for a structure that can easily prevent a user from inserting a gasoline fuel nozzle into a diesel fuel filler neck and vice versa.